To achieve this, build a JCI-Shortcode like [jsoncontentimporterpro url=http://….id=NUMBER_OF_ABOVE_TEMPLATE debugmode=10]
You might have to add authentication-info or similar data.
Publish the page and view it in ther browser. The browser should show you the debug-infos of the plugin and in the best case the RSS-code.
Then remove “debugmode=10” from the shortcode and publish the page again.
Add “?show=oc” to the browser. This should remove the template header, footer etc. and gives you the pure RSS-feed.